The art is replete with different types of biomedical electrodes which have an electrically conductive contacting tab. Examples of such biomedical electrodes are described in U.S. Pat. Nos. 4,543,958 to Cartmel, 4,798,208 to Faasse, Jr., 5,012,810 to Strand et al., 5,078,138 to Strand et al., 5,078,139 to Strand et al., 5,133,356 to Bryan et al., and 5,215,087 to Anderson, the entire contents of each of which are herein expressly incorporated by reference. Particular examples of such electrodes include 3M Red Dot.TM. ECG and EKG electrodes generally available from the Minnesota Mining and Manufacturing Co. (3M) of St. Paul., Minn. Typically, such electrodes have a substantially flat construction which leads to significant advantages including: (1) such an electrode is less conspicuous when worn under a patient's clothes and less obstructive to other medical procedures, and (2) the low profile of tab-style electrodes provides a structure which is free of any substantial projections that might cause discomfort for a patient should the patient be bumped in the vicinity of the electrode or should the patient lie on he electrode.
The art is also replete with connectors for electrically connecting medical equipment to a tab-style electrode. For example such medical equipment may comprise electrical signal receiving instrumentation, diagnostic equipment, stress monitoring equipment or other testing equipment for detecting a patient's electrical signals. Other examples of medical equipment include therapeutic electrical instrumentation such as transcutaneous electronic nerve stimulation (TENS) devices used for pain management and neuromuscular stimulation (NMS) equipment used for treating conditions such as scoliosis. Medical equipment may also include the equipment used in electrosurgery or equipment used with defibrillation pads for emergency cardiac treatment.
Examples of connectors for connecting medical equipment to a tab-style biomedical electrode include U.S. Pat. Nos. 4,061,408 to Bast et al., 4,555,155 to Drake, 4,700,997 to Strand, 4,842,558 to Strand, and 4,952,177 to Drake et al.
The art also includes "alligator" type electrical connectors. An "alligator" type electrical connector typically includes a fixed jaw and a movable jaw, a pin for mounting the movable jaw for pivotal movement relative to the fixed jaw between tab accept and closed positions and a spring for biasing the movable jaw toward the closed position. A leadwire is typically fixedly connected to the fixed jaw so that the fixed jaw does not move relative to the leadwire. As used herein, the term "fixed jaw" when used to describe one of the jaws of an "alligator" type connector, means that jaw which remains stationary or fixed relative to the leadwire when the connector is opened. Particular examples of "alligator" type electrical connectors include U.S. Pat. Nos. 3,090,029 to Stroebel, 3,644,877 to Carbonneau, 4,797,125 to Malana, 4,702,256 to Robinson et al., and 5,058,589 to Ding et al.
Prior art "alligator" type electrical connectors suffer from many drawbacks. In order to ensure a very high pull off force of the connector from the tab, some prior art "alligator" type electrical connectors include a very strong spring which renders the electrical connector difficult to open. Also, some prior art electrical connectors include a hole, depression, groove, slot, slit or other discontinuous surface in a jaw which is designed to deflect the tab of the electrode. Such deflection of the tab generally results in a higher grasping force for the tab but also tends to mar, puncture or otherwise damage the conductive surface of the electrically conductive contacting tab of the biomedical electrode. Such damage may potentially result in a loss of continuity or may otherwise adversely affect the electrical properties of the biomedical electrode.
Some jaws of prior art "alligator" electrical connectors include teeth, abutment surfaces, labyrinth-like or tortuous paths or an otherwise rough surfaces. A rough surface may include a structure that substantially deforms or deflects the electrode contacting tab during insertion of the tab into the connector. Again, the deflection of the tab into a surface irregularity may increase the tab pull off force of the connector, but not without costs. The rough surface may "catch" the electrically contacting tab and cause the contacting tab to bend or otherwise deform while the tab is being inserted into the connector. Such action may render the electrical connector difficult to place on the tab of an electrode.
Also, the V-shaped nature of many prior art "alligator" type connectors render them particularly susceptible to tangling with the leadwires of other leadwires and connectors as the leadwire of one assembly may easily slip between proximal ends of the fixed and movable jaws of another assembly.
Some existing prior art "alligator" type electrical connectors may be unsuitable for biomedical use as they have relatively sharp portions which may be uncomfortable for some patients. For example, should the patient roll on top of the connector, a sharp edge or tooth may cause discomfort for the patient.
Finally, U.S. patent application Ser. No. 07/990,692 filed Dec. 15, 1992 (naming Jerome E. Strand and Perry S. Dotterman as joint inventors) discloses an electrode connector comprising pivotally mounted fixed and movable jaws that are spring biased to a closed position. The jaws of that connector are mounted for pivotal movement by virtue of pins located on the movable jaw and recesses in the fixed jaw. While this connector functions adequately, its capacity to remain assembled could be improved.
That connector is assembled by 1) placing the spring between proximal end portions of the fixed and movable jaws, and 2) then sliding the movable jaw generally along the longitudinal axis of the fixed jaw until the pins of the movable jaw are seated in the recesses of the fixed jaw. The portions of the recesses in the fixed jaw that are adapted to receive the pins are larger than the pins in the movable jaw. Because of the shape and size of the recesses of the fixed jaw, it was possible to move the movable jaw downward relative to the fixed jaw when the jaws were assembled (e.g. such as when a user intended to open the jaws). Although it generally does not pose a problem, such downward movement of the movable jaw relative to the fixed jaw could lead to inadvertent disassembly of the assembled jaws, clearly an undesirable result.